Effects of Brain Stimulation During Nocturnal Sleep on Memory Consolidation in Patients With Mild Cognitive Impairments

Effects of Brain Stimulation During Nocturnal Sleep on Memory Consolidation in Patients With Mild Cognitive Impairments

Impact of Transcranial Slow Oscillating Stimulation on Memory Consolidation During Nocturnal Slow Wave Sleep in Patients With Mild Cognitive Impairments(MCI)

The beneficial effect of nocturnal sleep on memory consolidation is well-documented in young, healthy subjects. Especially, periods rich in slow-wave sleep (SWS) have shown a memory enhancing effect on hippocampus-dependent declarative memory. Slow oscillatory activity typically occuring during SWS has been implicated in the consolidation effect. Recent evidence in young healthy subjects suggest that the sleep-associated consolidation effect can be amplified by the application of a weak transcranial oscillatory electric current within the frequency range of SWS in humans (0,7-0,8 Hz) during SWS. If patients with amnestic mild cognitive impairments (MCI)- usually characterized by initial difficulties in hippocampus dependent memory functions - benefit from transcranial slow oscillatory stimulation (tSOS) during nocturnal sleep as well has not been studied so far. The primary aim of the present study is to investigate the influence of a weak slow oscillating brain stimulation (tSOS) on declarative memory consolidation applied during periods of nocturnal SWS in MCI patients.

mild cognitive impairment, dementia, MCI, brain stimulation, tSOS, tDCS, sleep, memory, memory consolidation

Retention of declarative memories after 0.75 Hz stimulation during SWS, vs after sham stimulation during SWS

Retention between stimulation conditions (0.75 Hz during SWS, vs sham stimulation during SWS) in the declarative memory task.

Amount of slow wave sleep assessed by standard polysomnographic criteria in 0,75 Hz vs SHAM stimulation during SWS. Spindel activity during sleep indicated via several spindel parameters like number, duration, frequency of spindles; compared between 0,75 Hz and SHAM stimulation during SWS. Neuronal correlates (EEG-power in slow oscillation frequency bands induced by 0,75 Hz vs SHAM stimulation during SWS; EEG-correlates of encoding and retrieval of a declarative memory task). Performance in further memory systems (procedural), compared between 0,75 Hz and SHAM stimulation during SWS.

Inclusion Criteria: amnestic and amnestic plus MCI-patients: Concern reflecting a change in cognition reported by patient or informant or clinician (i.e., historical or observed evidence of decline over time) Objective evidence of memory impairment; additional cognitive domains may be affected as well; Preservation of independence in functional abilities no dementia age: 50-90 years Exclusion Criteria: untreated severe internal or psychiatric diseases epilepsy other severe neurological diseases eg., previous major stroke, brain tumour dementia contraindications to MRI

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